Various apparatus are known for use in boring and cutting holes through workpieces. Conventional boring apparatus typically include a rotating cutting head which moves along an axis and into contact with a portion of a workpiece. These apparatus include a cutting blade extending forwardly from the cutting head and disposed generally parallel to and spaced from the axis to perform the cutting operation. The blade is positioned such that the rotation of the cutting head moves the blade along a circular path in a plane perpendicular to the axis. The hole is formed by advancing the cutting head along the axis towards the workpiece as it is rotated, until the cutting blade is moved completely through the workpiece.
A significant disadvantage of conventional boring tools is that both the hole which is formed, and the waste slug or plug which is cut from the workpiece, have side edges generally parallel to the axis. As a result, the waste slug or plug often falls through the hole into the workpiece. This is particularly undesirable where the tool is used to form holes in blow molded hollow workpieces, such as vehicle fuel tanks or the like, as the plugs are difficult to retrieve and must be manually removed. In an effort to prevent the slugs from falling into the workpiece, attempts have been made to cut tapered holes, such as disclosed in U.S. Pat. No. 5,653,560. Such devices, however, are expensive and complex, have numerous moving parts, often require computer feedback, and utilize large areas of space.
The apparatus described above are further disadvantageous in that they only allow for the cutting of holes in workpieces that are uniform or circular in shape. While various apparatus and techniques are known for cutting non-circular or arbitrary shaped holes in workpieces, they also suffer from a variety of significant disadvantages. First, these current apparatus and techniques require expensive technologies to control the operation of the cutting blade, such as CNC machinery, robot manipulation or other motion control or laser cutting. Additionally, current technologies for cutting non-circular holes generate chips during the cutting process. This also increases the cost of the process as it requires a separate vacuum step to remove any debris that has accumulated in the workpiece. This process also significantly increases the amount of time and expense required to cut holes in the workpiece.